Highly Sensitive Voltammetric Sensor Based on Catechol-Derivative-Multiwall Carbon Nanotubes for the Determination of Captopril in Urine Samples
A new catechol-derivative compound, N-(3,4-dihydroxyphenethyl)-3,5-dinitrobenzamide, was synthesized and used to construct a modified-carbon nanotubes paste electrode. The electro-oxidation of captopril at the surface of the modified electrode was studied using cyclic voltammetry, chronoamperometry, and electrochemical impedance spectroscopy. Under the optimized conditions, the differential pulse voltammetric peak current of captopril increased linearly with captopril concentration in the ranges of 6.4 × 10−8 to 3.2 × 10−48 mol L−1. The detection limit was 3.4 × 10−8 mol L−1 captopril. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) for captopril oxidation were also determined. The RSD% for 0.5 and 10.0 μmol L−1 captopril were 2.1% and 1.6%, respectively. The proposed sensor was successfully applied for the determination of captopril in human patient urine and tablet samples.